linux-kernel - Re: [PATCH 0/4 V15] Avoid soft lockup message when KVM is stopped by host

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Date:	Fri, 02 Mar 2012 14:23:55 -0800
From:	Eric B Munson <emunson@...bm.net>
To:	<avi@...hat.com>
Cc:	<mingo@...hat.com>, <hpa@...or.com>, <ryanh@...ux.vnet.ibm.com>,
	<aliguori@...ibm.com>, <mtosatti@...hat.com>,
	<kvm@...r.kernel.org>, <linux-arch@...r.kernel.org>,
	<x86@...nel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4 V15] Avoid soft lockup message when KVM is stopped
 by host

On Sun, 19 Feb 2012 21:22:53 -0500, Eric B Munson wrote:
> Changes from V14:
> Update documentation for the pvclock api

... snip

>
> When a guest kernel is stopped by the host hypervisor it can look 
> like a soft
> lockup to the guest kernel.  This false warning can mask later soft 
> lockup
> warnings which may be real.  This patch series adds a method for a 
> host
> hypervisor to communicate to a guest kernel that it is being stopped. 
> The
> final patch in the series has the watchdog check this flag when it 
> goes to
> issue a soft lockup warning and skip the warning if the guest knows 
> it was
> stopped.
>
> It was attempted to solve this in Qemu, but the side effects of 
> saving and
> restoring the clock and tsc for each vcpu put the wall clock of the
> guest behind
> by the amount of time of the pause.  This forces a guest to have ntp 
> running
> in order to keep the wall clock accurate.

Avi,

Is this version acceptable for merging?  I'd really like this to go in 
for the 3.4 merge window.

Thanks,
Eric

>
> Cc: mingo@...hat.com
> Cc: hpa@...or.com
> Cc: ryanh@...ux.vnet.ibm.com
> Cc: aliguori@...ibm.com
> Cc: mtosatti@...hat.com
> Cc: kvm@...r.kernel.org
> Cc: linux-arch@...r.kernel.org
> Cc: x86@...nel.org
> Cc: linux-kernel@...r.kernel.org
>
> Eric B Munson (4):
>   Add flag to indicate that a vm was stopped by the host
>   Add functions to check if the host has stopped the vm
>   Add ioctl for KVM_KVMCLOCK_CTRL
>   Add check for suspended vm in softlockup detector
>
>  Documentation/virtual/kvm/api.txt   |   20 ++++++++++++++++++++
>  Documentation/virtual/kvm/msr.txt   |    4 ++++
>  arch/ia64/include/asm/kvm_para.h    |    5 +++++
>  arch/powerpc/include/asm/kvm_para.h |    5 +++++
>  arch/s390/include/asm/kvm_para.h    |    5 +++++
>  arch/x86/include/asm/kvm_para.h     |    8 ++++++++
>  arch/x86/include/asm/pvclock-abi.h  |    1 +
>  arch/x86/kernel/kvmclock.c          |   21 +++++++++++++++++++++
>  arch/x86/kvm/x86.c                  |   22 ++++++++++++++++++++++
>  include/asm-generic/kvm_para.h      |   14 ++++++++++++++
>  include/linux/kvm.h                 |    3 +++
>  kernel/watchdog.c                   |   12 ++++++++++++
>  12 files changed, 120 insertions(+), 0 deletions(-)
>  create mode 100644 include/asm-generic/kvm_para.h

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